Integrated circuits are typically formed from a substrate over which are formed patterned microelectronics layers. In the processing of the substrate, plasma is often employed to deposit films on the substrate or to etch intended portions of the films. Shrinking feature sizes and implementation of new materials in next generation microelectronics layers have put new demands on plasma processing equipment. The smaller features, larger substrate size and new processing techniques create additional demands on control of the plasma parameters, such as plasma density and etch uniformity across the substrate, to achieve desired yields.
In capacitively coupled RF plasma reactors, the electrode opposite to the substrate electrode is generally called the upper electrode. The upper electrode could be grounded, or have one or more radio frequency (RF) power sources attached to it. The substrate electrode is generally called the lower electrode. A mechanical arrangement for a lower electrode in a capacitively coupled plasma processing chamber may involve cantilevering the assembly that includes the lower electrode from a side of the chamber. This cantilevered lower electrode can be a fixed distance from the upper electrode or can be designed for a variable distance from the upper electrode. In either case, planarization of the lower electrode may be affected by sag and RF interference can occur when service conduits to the chuck are located in the interior of the cantilever support arm.
A cantilevered lower electrode assembly to increase planarity control between the upper and lower electrodes is disclosed in commonly-owned U.S. Patent Publication No. 2009/0199766, the disclosure of which is hereby incorporated by reference. While the '766 publication discloses an improved sidewall supported substrate support, due to the need to address smaller substrate features, larger substrate sizes, and new processing techniques, there is a need for improved gap height and planarity control between the upper and lower electrodes to increase etch uniformity across the substrate.